The present invention relates generally to operating electrical and/or mechanical devices based upon the more accurate solar day. More particularly, the present invention relates to controlling devices relative to the accurate rotation of the earth and the actual sunrise and sunset of the day, which is critical and essential to some safety conditions, religious institutions, irrigation, aquiculture , and other industries.
Previous multipurpose event timers have been based almost entirely on the time of day. These conventional events times include both traditional time and daylight-saving time. The assumption is made that sunrise and sunset occur daily at approximately 6:00 A.M. and 6:00 P.M. respectively. This assumption for sunrise and sunset divides a 24 hour period neatly in half but it does not reflect the reality that sunrise and sunset times vary widely.
These conventional event timers also assume that the actual solar earth rotation and the associated actual sunrise and sunset are not critical. The solar day is based on the time it takes the earth to make one complete rotation referenced to fixed stars instead of the sun. The solar period is 23 hours, 53 minutes and 4.09 seconds (23.9515 hours).
Industrial safety at night is an example of an area where a solar timer can be effectively used. Safety lighting is a world-wide multimillion dollar expense for businesses. For example, lighting needs to be provided in times of darkness or during a part of the night. It is wasteful to turn safety lights on before it is dark, and equally wasteful to leave them on when they are not needed. Since the time of day for sunrise and sunset is constantly changing every day of the year, it is difficult to approximate the actual time of day for each day to activate a safety light. Schools and business are also affected by this daily problem. If a conventional timer is used for these applications, then a person must periodically adjust the timer to ensure that the desired event occurs at the appropriate time after darkness.
Some industries and agricultural businesses time events around the rising and setting sun. It is known that fish, for example, feed very heavily at sunrise and sunset, although they are also known to feed rather continuously all day. Some commercial fisheries have learned that feeding just after sunrise and just before sunset is much more efficient in terms of maximum weight gain of fish per pound of feed. Additionally, in a zoo or similar habitat, there are certain animals which feed nocturnally. It can be burdensome for humans to have to feed such animals in the middle of the night. There is an advantage to be able to automate the feeding of such nocturnal animals without human invention.
Irrigation is another area where an accurate timer can be helpful. In some situations it is important to water crops or gardens after sunset. In arid areas, this allows the water to soak into the target area during darkness. Since the actual time of sunset varies, it is helpful to have a system that adjusts the watering time relative to sunset. An automatic self adjusting system has been difficult in the prior art because of the fixed timers that have conventionally been used.
Another problem with the prior art is that many event timers or controllers stop completely when the power fails, or they are reset to some predetermined starting time (e.g. 12:00 A.M.) after a power failure. This results in a timed or controlled event happening at the wrong time of day. For example, a safety light can come on in the daylight or before or after a work shift was completed.
Some conventional timers are computer controlled and are able to correct or reset themselves to the correct time of day after a power failure. Other timers even have elaborate UPS and battery systems to avoid computer shutdown in the event of a power loss. The problem with computer controlled or UPS timer systems is the expense and complexity. Many controllers come with extremely complicated hardware, ladder networks, interfaces, and programming systems.
It is desirable to provide a system which would provide control for electrical and mechanical devices based upon a more accurate timing system. It would also be advantageous to provide a timer which is keyed to the actual sunrise or sunset of each day.
It has been recognized that it would be advantageous to develop a solar event timer. The solar event timer includes an optical sensor to determine when daylight begins and ends. A solar counter is loaded with a number of solar units in a day. A clock is coupled to the solar counter and optical sensor, and is configured to linearly count down solar units during daylight and to county down the solar units at night at an accelerated rate. Electronic circuitry is included to trigger an event when the solar counter reaches zero.